Low-level derivations: Difference between revisions

Line 15:

args = [

"-c"

"echo '#!/bin/bash' </nowiki>><nowiki> $out"

''

"echo 'echo \"Hello, World!\"' </nowiki>><nowiki> $out"

echo '#!/bin/bash' </nowiki>><nowiki> $out

"chmod +x $out"

echo 'echo "Hello, World!"' </nowiki>>><nowiki> $out

chmod +x $out

''

];

}</nowiki>}}There are a number of elements in this Nix file, but remembering the conceptual model of a framework makes quick work of figuring them out: a derivation is a set of ''inputs along with an executable'' that produces a deterministic ''output'', following a list of ''steps.'' Here our inputs are quite literally the key-value pairs in the derivation [[Attribute set|attrset]]: the <code>name</code> of the derivation and the system it's being built ''for''. The executable (called the builder) is the program found at <code>/bin/bash</code>. And the steps are:

}</nowiki>}}There are a number of elements in this Nix file, but remembering the conceptual model of a framework makes quick work of figuring them out: a derivation is a set of ''inputs along with an executable'' that produces a deterministic ''output'', following a list of ''steps.'' Here our inputs are quite literally the key-value pairs in the derivation [[Attribute set|attrset]]: the <code>name</code> of the derivation and the system it's being built ''for''. The executable (called the <code>builder</code>) is the program found at <code>/bin/bash</code>. And the steps are:

# Write the string <code>#!/bin/bash</code> to the output file (<code>$out</code>);

# Write the string <code>echo "Hello, World!"</code> to the output file;

# Make the output file executable.

@@ Line 15: / Line 15: @@
    args = [
      "-c"
-     "echo '#!/bin/bash' </nowiki>><nowiki> $out"
+     ''
-    "echo 'echo \"Hello, World!\"' </nowiki>><nowiki> $out"
+      echo '#!/bin/bash' </nowiki>><nowiki> $out
-    "chmod +x $out"
+      echo 'echo "Hello, World!"' </nowiki>>><nowiki> $out
+      chmod +x $out
+    ''
    ];
-}</nowiki>}}There are a number of elements in this Nix file, but remembering the conceptual model of a framework makes quick work of figuring them out: a derivation is a set of ''inputs along with an executable'' that produces a deterministic ''output'', following a list of ''steps.'' Here our inputs are quite literally the key-value pairs in the derivation [[Attribute set|attrset]]: the <code>name</code> of the derivation and the system it's being built ''for''. The executable (called the builder) is the program found at <code>/bin/bash</code>. And the steps are:
+}</nowiki>}}There are a number of elements in this Nix file, but remembering the conceptual model of a framework makes quick work of figuring them out: a derivation is a set of ''inputs along with an executable'' that produces a deterministic ''output'', following a list of ''steps.'' Here our inputs are quite literally the key-value pairs in the derivation [[Attribute set|attrset]]: the <code>name</code> of the derivation and the system it's being built ''for''. The executable (called the <code>builder</code>) is the program found at <code>/bin/bash</code>. And the steps are:
 # Write the string <code>#!/bin/bash</code> to the output file (<code>$out</code>);
 # Write the string <code>echo "Hello, World!"</code> to the output file;
 # Make the output file executable.